The delivery of a beneficial drug in the colon is therapeutically indicated for the treatment of inflammatory bowel disease, colitis ulcerosa, enteritis regionalis Crohn, chronic nonspecific colitis and diverticulitis. A critical and a pressing need exists for a dosage form for orally administering a beneficial drug for the management of these diseases and ailments of the colon. An oral dosage form is needed and it would be of a particular value in the management of disease and ailments of the colon that require colon-targeted delivery of a beneficial drug. Specifically, the dosage form would have a therapeutic value where therapy indicates the need for local, topical colon delivery of a beneficial drug to an affected colon site.
Prior to this invention tablets, capsules, and the like, were orally administered for delivering a beneficial drug to the colon. However, these prior art dosage forms delivered the drug throughout the entire length of the gastrointestinal tract. Moreover, the prior art dosage forms suffered with some disadvantages. For example, for some drugs a considerable amount of the drug dispensed by tablets and capsules is inactivated by the stomach because of the acidic and enzymatic environment of the stomach. Consequently the drug never reaches the colon to produce its intended effect. Additionally, most drug are metabolized or absorbed in the small intestine from such immediate release or sustained release forms. Thus, very little of the drug is available for producing a therapeutic result in the colon. The delivery of a drug through the rectum using suppositories, or by an enema, often leads to colon therapy, but rectal administration is inconvenient and messy and it is not readily accepted by the patient population. Also, drug delivery from suppositories cannot reach most of the colon as suppositories are self-limiting to the immediate area of administration.
In view of the above presentation it is immediately self-evident that a need exists for an oral dosage form that delays the onset of delivery for a period of time for the dosage form to reach the colon. Such a period of time corresponds to the time required for the dosage form to transit through the stomach and the small intestine and then commence delivery of a drug about the time the dosage form arrives at the colon.